1. Field of the Invention
The present invention relates generally to methods of controlling the viscosity of fluids. Specifically, the invention relates to a method of controlling the viscosity of a fluid in a defined volume by heating the inner surfaces of the volume through the use of a heater element such as a heater element laminated composite in the form of a thin, laminated material applied to the surface.
2. Description of the Prior Art
It is well known that the viscosity of a liquid is a function of the liquid temperature. It follows that heating the inner surface of a volume containing a liquid, such as the interior of a pipe or tank, will alter the viscosity of the liquid.
A variety of methods for heating surfaces through the use of heater elements exist in the prior art. U.S. Pat. No. 4,534,886, to Kraus et al., discloses an electrically conductive web composed of a non-woven sheet of conductive fibers and non-conductive fibers. The sheet is saturated with a dispersion containing conductive particles and dried. The Kraus et al. heater element is primarily used in heating pads.
International Application No. PCT/US94/13504 (Publication No. WO95/15670), discloses an electrically conductive composite heating assembly that has an electrically conductive non-woven fiber layer laminated between layers of fiberglass and other dielectric material. The assembly further has an abrasion resistant outer layer. The heater element is used on aerospace structures as an ice protection system to withstand repeated mechanical stress and thermal cycles in extremely harsh aerospace environments.
U.S. Pat. No. 5,344,696 to Hastings et al. discloses an integrally bonded laminate which is used to thermally control a surface or portion of a surface of an aircraft to which the laminate is bonded.
None of the prior art heater elements, however, have been successfully applied to the surface of a defined volume for the purpose of controlling the viscosity of the fluid contained therein.